Method for the vapor-phase carbonylation of lower aliphatic alcohols using a supported platinum catalyst and halide promoter

ABSTRACT

A method for the vapor-phase carbonylation of lower alkyl alcohols to esters and optionally, carboxylic acids using a catalyst having a platinum on a solid support material as a first component and a vaporous halide as a second component. Desirably, the catalyst includes platinum on an activated carbon support and the vaporous halide is selected from hydrogen halides, alkyl halides and aryl halides having up to 12 carbon atoms, and mixtures thereof.

FIELD OF THE INVENTION

The present invention relates to a method for the vapor phasecarbonylation of alkyl alcohols, ethers, esters and ester-alcoholmixtures to produce esters and carboxylic acids and particularly, thecarbonylation of methanol to produce acetic acid and methyl acetate.More particularly, the present invention relates to the vapor-phasecarbonylation of methanol to produce acetic acid and methyl acetateusing a catalyst which includes a solid component having platinumassociated with a solid support material and a vaporous halidecomponent.

BACKGROUND OF THE INVENTION

Lower carboxylic acids and esters such as acetic acid and methyl acetatehave been known as industrial chemicals for many years. Acetic acid isused in the manufacture of a variety of intermediary and end-products.For example, an important derivative is vinyl acetate which can be usedas monomer or co-monomer for a variety of polymers. Acetic acid itselfis used as a solvent in the production of terephthalic acid, which iswidely used in the container industry, and particularly in the formationof PET beverage containers.

There has been considerable research activity in the use of metalcatalysts for the carbonylation of lower alkyl alcohols, such asmethanol, and ethers to their corresponding carboxylic acids and esters,as illustrated in equations 1-3 below:

    ROH+CO→RCOOH                                        (1)

    2ROH+CO→RCOOR+water                                 (2)

    ROR'+CO→RCOOR                                       (3)

Carbonylation of methanol is a well known reaction and is typicallycarried out in the liquid phase with a catalyst. A thorough review ofthese commercial processes and other approaches to accomplishing theformation of acetyl from a single carbon source is described by Howardet al. in Catalysis Today, 18, 325-254 (1993). Generally, the liquidphase carbonylation reactions for the preparation of acetic acid usingmethanol are performed using homogeneous catalyst systems comprising aGroup VIII metal and iodine or an iodine-containing compound such ashydrogen iodide and/or methyl iodide. Rhodium is the most common GroupVIII metal catalyst and methyl iodide is the most common promoter. Thesereactions are conducted in the presence of water to preventprecipitation of the catalyst.

U.S. Pat. No. 5,144,068 describes the inclusion of lithium in thecatalyst system which allows the use of less water in the Rh-Ihomogeneous process. Iridium also is an active catalyst for methanolcarbonylation reactions but normally provides reaction rates lower thanthose offered by rhodium catalysts when used under otherwise similarconditions.

U.S. Pat. No. 5,510,524 teaches that the addition of rhenium improvesthe rate and stability of both the Ir-I and Rh-I homogeneous catalystsystems.

European Patent Application EP 0 752 406 A1 teaches that ruthenium,osmium, rhenium, zinc, cadmium, mercury, gallium, indium, or tungstenimprove the rate and stability of the liquid phase Ir-I catalyst system.Generally, the homogeneous carbonylation processes presently being usedto prepare acetic acid provide relatively high production rates andselectivity. However, heterogeneous catalysts offer the potentialadvantages of easier product separation, lower cost materials ofconstruction, facile recycle, and even higher rates.

Schultz, in U.S. Pat. No. 3,689,533, discloses using a supported rhodiumheterogeneous catalyst for the carbonylation of alcohols to formcarboxylic acids in a vapor phase reaction. Schultz further disclosesthe presence of a halide promoter.

Schultz in U.S. Pat. No. 3,717,670 describes a similar supported rhodiumcatalyst in combination with promoters selected from Groups IB, IIIB,IVB, VB, VIB, VIII, lanthanide and actinide elements of the PeriodicTable.

Uhm, in U.S. Pat. No. 5,488,143, describes the use of alkali, alkalineearth or transition metals as promoters for supported rhodium for thehalide-promoted, vapor phase methanol carbonylation reaction. Pimblett,in U.S. Pat. No. 5,258,549, teaches that the combination of rhodium andnickel on a carbon support is more active than either metal by itself.

In addition to the use of iridium as a homogeneous alcohol carbonylationcatalyst, Paulik et al., in U.S. Pat. No. 3,772,380, describe the use ofiridium on an inert support as a catalyst in the vapor phase,halogen-promoted, heterogeneous alcohol carbonylation process.

European Patent Applications EP 0 120 631 A1 and EP 0 461 802 A2describe the use of special carbons as supports for single transitionmetal component carbonylation catalysts.

European Patent Application EP 0 759 419 A1 pertains to a process forthe carbonylation of an alcohol and/or a reactive derivative thereof.

EP 0 759 419 A1 discloses a carbonylation process comprising a firstcarbonylation reactor wherein an alcohol is carbonylated in the liquidphase in the presence of a homogeneous catalyst system and the off gasfrom this first reactor is then mixed with additional alcohol and fed toa second reactor containing a supported catalyst. The homogeneouscatalyst system utilized in the first reactor comprises a halogencomponent and a Group VIII metal selected from rhodium and iridium. Whenthe Group VIII metal is iridium, the homogeneous catalyst system alsomay contain an optional co-promoter selected from the group consistingof ruthenium, osmium, rhenium, cadmium, mercury, zinc, indium andgallium. The supported catalyst employed in the second reactor comprisesa Group VIII metal selected from the group consisting of iridium,rhodium, and nickel, and an optional metal promoter on a carbon support.The optional metal promoter may be iron, nickel, lithium and cobalt. Theconditions within the second carbonylation reactor zone are such thatmixed vapor and liquid phases are present in the second reactor. Thepresence of a liquid phase component in the second reactor inevitablyleads to leaching of the active metals from the supported catalystwhich, in turn, results in a substantial decrease in the activity of thecatalyst.

The literature contains several reports of the use of rhodium-containingzeolites as vapor phase alcohol carbonylation catalysts at one barpressure in the presence of halide promoters. The lead references onthis type of catalyst are presented by Maneck et al. in Catalysis Today,3, 421-429 (1988),. Gelin et al., in Pure & Appl. Chem., Vol 60, No. 8,1315-1320 (1988), provide examples of the use of rhodium or iridiumcontained in zeolite as catalysts for the vapor phase carbonylation ofmethanol in the presence of halide promoter. Krzywicki et al., inJournal of Molecular Catalysis, 6, 431-440 (1979), describe the use ofsilica, alumina, silica-alumina and titanium dioxide as supports forrhodium in the halide-promoted vapor phase carbonylation of methanol,but these supports are generally not as efficient as carbon. Luft etal., in U.S. Pat. No. 4,776,987 and in related disclosures, describe theuse of chelating ligands chemically attached to various supports as ameans to attach Group VIII metals to a heterogeneous catalyst for thehalide-promoted vapor phase carbonylation of ethers or esters tocarboxylic anhydrides.

Evans et al., in U.S. Pat. No. 5,185,462, describe heterogeneouscatalysts for halide-promoted vapor phase methanol carbonylation basedon noble metals attached to nitrogen or phosphorus ligands attached toan oxide support.

Panster et al., in U.S. Pat. No. 4,845,163, describe the use ofrhodium-containing organopolysiloxane-ammonium compounds asheterogeneous catalysts for the halide-promoted liquid phasecarbonylation of alcohols.

Drago et al., in U.S. Pat. No. 4,417,077, describe the use of anionexchange resins bonded to anionic forms of a single transition metal ascatalysts for a number of carbonylation reactions including thehalide-promoted carbonylation of methanol. Although supported ligandsand anion exchange resins may be of some use for immobilizing metals inliquid phase carbonylation reactions, in general, the use of supportedligands and anion exchange resins offer no advantage in the vapor phasecarbonylation of alcohols compared to the use of the carbon as a supportfor the active metal component.

Nickel on activated carbon has been studied as a heterogeneous catalystfor the halide-promoted vapor phase carbonylation of methanol. Relevantreferences to the nickel-on-carbon catalyst systems are provided byFujimoto et al. in Chemistry Letters 895-898, (1987). Moreover, Fujimotoet al. in Journal of Catalysis, 133, 370-382 (1992) observed increasedrates when hydrogen is added to the feed mixture. Liu et al., in Ind.Eng. Chem. Res., 33 488-492, (1994), report that tin enhances theactivity of the nickel-on-carbon catalyst. Mueller et al., in U.S. Pat.No. 4,918,218, disclose the addition of palladium and optionally copperto supported nickel catalysts for the halide-promoted carbonylation ofmethanol. In general the rates of reaction provided by nickel-basedcatalysts are lower than those provided by the analogous rhodium-basedcatalysts when operated under similar conditions.

Other single metals supported on carbon have been reported by Fujimotoet al. in Catalysis Letters, 2, 145-148 (1989) to have limited activityin the halide-promoted vapor phase carbonylation of methanol. The mostactive of these metals is Sn. Following Sn in order of decreasingactivity are Pb, Mn, Mo, Cu, Cd, Cr, Re, V, Se, W, Ge and Ga. None ofthese other single metal catalysts are nearly as active as those basedon Rh, Ir, Ni or the catalyst of the present invention.

Yagita and Fujimoto in Journal of Molecular Catalysis, 69, 191-197(1991) examined the role of activated carbon in a metal supportedcatalyst and observed that the carbonylation activities of Group VIIImetals supported on activated carbon are ordered by the affinitiesbetween the metal and the halogen.

A number of solid materials have been reported to catalyze thecarbonylation of methanol without the addition of the halide promoter.Gates et al., in Journal of Molecular Catalysis, 3, 1-9 (1977/78)describe a catalyst containing rhodium attached to polymer boundpolychlorinated thiophenol for the liquid phase carbonylation ofmethanol. Current, in European Patent Application EP 0 130 058 A1,describes the use of sulfided nickel containing optional molybdenum as aheterogeneous catalyst for the conversion of ethers, hydrogen and carbonmonoxide into homologous esters and alcohols.

Smith et al., in European Patent Application EP 0 596 632 A1, describethe use of mordenite zeolite containing Cu, Ni, Ir, Rh, or Co ascatalysts for the halide-free carbonylation of alcohols. Feitler, inU.S. Pat. No. 4,612,387, describes the use of certain zeolitescontaining no transition metals as catalysts for the halide-freecarbonylation of alcohols and other compounds in the vapor phase.

U.S. Pat. No. 5,218,140, describes a vapor phase process for convertingalcohols and ethers to carboxylic acids and esters by the carbonylationof alcohols and ethers with carbon monoxide in the presence of a metalion exchanged heteropoly acid supported on an inert support. Thecatalyst used in the reaction includes a polyoxometallate anion in whichthe metal is at least one of a Group V(a) and VI(a) is complexed with atleast one Group VIII cation such as Fe, Ru, Os, Co, Rh, Ir, Ni, Pd or Ptas catalysts for the halide-free carbonylation of alcohols and othercompounds in the vapor phase.

The present invention for the vapor-phase carbonylation of alkylalcohols, ethers, esters and ester-alcohol mixtures to produce estersand carboxylic acids and particularly, the carbonylation of methanol toproduce acetic acid and methyl acetate represents the firstdemonstration of a method using a catalyst having platinum as the soleactive metal component in the heterogeneous catalyst prior art. The useof platinum as a carbonylation catalyst would be beneficial sinceplatinum compounds are both less volatile and less soluble relative toother active catalysts, such as Ir and Rh, and therefore are less likelyto be removed from the catalyst support during operation of thecarbonylation process.

SUMMARY OF THE INVENTION

Briefly, the present invention provides a method for vapor-phasecarbonylation for producing esters and carboxylic acids from reactantscomprising lower alkyl alcohols, ethers, esters, and mixtures ofester-alcohols. The method includes contacting the reactants with acatalyst having a solid first component which includes platinum on asolid support material and a halide vaporous second component.

It is an object of the invention to provide a method for thecarbonylation of lower alkyl alcohols, esters, ethers and ester-alcoholmixtures to produce esters and carboxylic acids. More particularly, itis an object of the present invention to provide a method forvapor-phase carbonylation of lower alkyl alcohols, ethers, esters andester-alcohol mixtures to produce carboxylic acids and esters, andparticularly acetic acid and methyl acetate.

It is another object of the present invention to provide a method forthe vapor-phase carbonylation of methanol using a heterogeneous catalysthaving platinum associated with a solid support and a vapor component.

It is another object of the invention to provide a process in which thecatalyst is maintained in a solid phase to reduce or eliminate thehandling losses of the catalyst.

It is another object of the invention to provide a vapor phasecarbonylation process for the production of acetic acid and methylacetate which utilizes a more stable catalyst and reduces the need forcatalyst recovery and recycle as well as solvent recovery.

These and other objects and advantages of the invention will becomeapparent to those skilled in the art from the accompanying detaileddescription.

DETAILED DESCRIPTION OF THE INVENTION

A vapor-phase carbonylation method for the continuous production ofcarboxylic acids and esters is provided by reacting lower alkylalcohols, ethers and ester-alcohol mixtures with a catalyst having asolid first component and vapor-phase second component. In a preferredembodiment of the invention, a vapor-phase carbonylation method for thecontinuous production of acetic acid or methyl acetate is provided. Themethod or carbonylation process is operated in the vapor state and,therefore, is practiced at temperatures above the dew point of theproduct mixture, i.e., the temperature at which condensation occurs.However, since the dew point is a complex function of dilution(particularly with respect to non-condensable gases such as unreactedcarbon monoxide, hydrogen, or inert diluent gas), product composition,and pressure, the process may still be operated over a wide range oftemperatures, provided the temperature exceeds the dew point of theproduct effluent. In practice, this generally dictates a temperaturerange of about 100° C. to 500° C., with temperatures in the range of100° C. to 325° C. being preferred and temperature of about 150° C. to275° C. being more preferred. Operating in the vapor phase isadvantageous since it eliminates catalyst dissolution, i.e., metalleaching from the catalyst support, which occurs in the knownheterogeneous processes operating in the presence of liquid compounds.

As with temperature, the useful pressure range is limited by the dewpoint of the product mixture. However, provided that the reaction isoperated at a temperature sufficient to prevent liquefaction of theproduct effluent, a wide range of pressures may be used, e.g., pressuresin the range of about 0.1 to 100 bars absolute. The process preferablyis carried out at a pressure in the range of about 1 to 50 barsabsolute, most preferably, about 3 to 30 bar absolute.

Suitable feedstock for the carbonylation process include lower alkylalcohols, ethers, ester-alcohol mixtures and, as more fully discussedbelow esters, which may be carbonylated in accordance with the presentinvention. Non-limiting examples include alcohols and ethers in which analiphatic carbon atom is directly bonded to an oxygen atom of either analcoholic hydroxyl group in the compound or an ether oxygen in thecompound and may further include aromatic moieties. Preferably, thefeedstock is one or more lower alkyl alcohols having from 1 to 10 carbonatoms and preferably having from 1 to 6 carbon atoms, alkane polyolshaving 2 to 6 carbon atoms, alkyl alkylene polyethers having 3 to 20carbon atoms and alkoxyalkanols having from 3 to 10 carbon atoms. Themost preferred reactant is methanol. Although methanol is preferablyused in the process and is normally fed as methanol, it can be suppliedin the form of a combination of materials which generate methanol.Examples of such combination of materials include (i) methyl acetate andwater and (ii) dimethyl ether and water. In the operation of theprocess, both methyl acetate and dimethyl ether are formed within thereactor and, unless methyl acetate is the desired product, they arerecycled with water to the reactor where they are later consumed to formacetic acid. Accordingly, one skilled in the art will further recognizethat it is possible to utilize the present invention to produce acarboxylic acid from an ester feed material.

Although the presence of water in the gaseous feed mixture is notessential when using methanol, the presence of some water is desirableto suppress formation of methyl acetate and/or dimethyl ether. Whenusing methanol to generate acetic acid, the molar ratio of water tomethanol can be 0:1 to 10:1, but preferably is in the range of 0.01:1 to1:1. When using an alternative source of methanol such as methyl acetateor dimethyl ether, the amount of water fed usually is increased toaccount for the mole of water required for hydrolysis of the methanolalternative. Accordingly, when using either methyl acetate or dimethylether, the mole ratio of water to ester or ether is in the range of 1:1to 10:1, but preferably in the range of 1:1 to 3:1. In the preparationof acetic acid, it is apparent that combinations of methanol, methylester, and/or dimethyl ether are equivalent, provided the appropriateamount of water is added to hydrolyze the ether or ester to provide themethanol reactant.

When the process is operated to produce methyl acetate, no water shouldbe added and dimethyl ether becomes the preferred feedstock. Further,when methanol is used as the feedstock in the preparation of methylacetate, it is necessary to remove water. However, the primary utilityof the process of the present invention is in the manufacture of aceticacid.

In the practice of the process of the invention, the lower alkylalcohol, ester, and/or ether in the vapor phase is passed through orover a catalyst having a solid phase first component and a vapor phasesecond component. The solid phase component of the catalyst includesplatinum associated with a substantially inert solid support. The formof platinum used to prepare the catalyst generally is not critical. Thesolid phase component of the catalyst may be prepared from a widevariety of platinum containing compounds and can be in the form of asalt of a mineral acid halide, such as chloroplatinic acid; trivalentnitrogen compounds such as dichlorodiammine platinum; organic compoundsof trivalent phosphorous, such as dichlorobis(triphenylphosphine)platinum; olefins, such as dichloro(1,5-cyclooctadiene) platinum;nitrites, such as dichlorobis(bezonitrile) platinum and oxides ofplatinum may be used if dissolved in the appropriate medium either aloneor in combination. The preferred sources of platinum is one of itchlorides, such as any of the various salts of hexachloroplatinate(IV)or a solution of platinum dichloride in either aqueous HCl of aqueousammonia.

The amount of platinum, as metal, on the support can vary from about0.01 weight percent to about 10 weight percent, with from about 0.1weight percent to about 2 weight percent platinum being preferred.

The solid support useful for acting as a carrier for the platinumconsists of a porous solid of such size that it can be employed in fixedor fluidized bed reactors. Typical support materials have a size of fromabout 400 mesh per inch to about 1/2 inch. Preferably, the support iscarbon, including activated carbon, having a high surface area.Activated carbon is well known in the art and may be derived from coalor peat having a density of from about 0.03 grams/cubic centimeter(g/cm³) to about 2.25 g/cm³. The carbon can have a surface area of fromabout 200 square meters/gram (m² /g) to about 1200 m² /g. Other solidsupport materials which may be used in accordance with the presentinvention include pumice, alumina, silica, silica-alumina, magnesia,diatomaceous earth, bauxite, titania, zirconia, clays, magnesiumsilicate, silicon carbide, zeolites, and ceramics. The shape of thesolid support is not particularly important and can be regular orirregular and include extrudates, rods, balls, broken pieces and thelike disposed within the reactor.

The platinum can be associated with the solid support by solubilizing,dispersing or suspending the platinum a suitable solvent or liquidvehicle and contacting the platinum solution, dispersion or suspensionwith the desired solid support. The liquid is evaporated, i.e. the solidsupport is dried so that at least a portion of the platinum isassociated with the solid support. Drying temperatures can range fromabout 100° C. to about 600° C. for a period greater than about onesecond. One skilled in the art will understand that the drying time isdependent upon the temperature, humidity, and solvent used. Generally,lower temperatures require longer heating periods to effectivelyevaporate the solvent from the solid support.

The catalyst system further includes at least one halide vapor componentselected from chlorine, bromine and iodine and preferably, the halidecompound is selected from bromine, iodine and mixtures thereof, whichare vaporous under vapor-phase carbonylation conditions of temperatureand pressure. Suitable halides include hydrogen halides such as hydrogeniodide and gaseous hydriodic acid; alkyl and aryl halides having up to12 carbon atoms such as, methyl iodide, ethyl iodide, 1-iodopropane,2-iodobutane, 1-iodobutane, methyl bromide, ethyl bromide, benzyl iodideand mixtures thereof. Desirably, the halide is a hydrogen halide or analkyl halide having up to 6 carbon atoms. Non-limiting examples ofpreferred halides include hydrogen iodide, methyl iodide, hydrogenbromide, methyl bromide and mixtures thereof. The halide may also be amolecular halide such as I₂, Br₂, or Cl₂.

The molar ratio of methanol or methanol equivalents to halide present toproduce an effective carbonylation ranges from about 1:1 to 10,000:1,with the preferred range being from about 5:1 to about 1000:1.

In a preferred aspect of the invention, the vapor-phase carbonylationcatalyst may be used for making acetic acid, methyl acetate or mixturesthereof. The process includes the steps of contacting a gaseous mixturecomprising methanol and carbon monoxide with a catalyst system in acarbonylation zone and recovering a gaseous product from thecarbonylation zone. The catalyst system includes a solid-phase componentcomprising platinum deposited on a carbon support and a vapor-phasecomponent comprising at least one halide described above.

Carbon monoxide may be fed to the carbonylation zone either as purifiedcarbon monoxide or as a mixture of hydrogen and carbon monoxide.Although hydrogen is not part of the reaction stoichiometry, hydrogenmay be useful in maintaining optimal catalyst activity. The preferredratio of carbon monoxide to hydrogen generally ranges from about 99:1 toabout 2:1, but ranges with even higher hydrogen levels are also likelyto be useful.

The present invention is illustrated in greater detail by the specificexamples presented below. It is to be understood that these examples areillustrative embodiments and are not intended t be limiting of theinvention, but rather are to be construed broadly within the scope andcontent of the appended claims.

In the examples which follow all of the catalysts were prepared in asimilar manner except as specified otherwise.

EXAMPLE 1

A solid supported platinum catalyst was prepared by mixing 569milligrams (mg) of dihydrogen hexachloroplatinate (chloroplatinic acid)having a platinum assay of 40%, (1.17 mmol of Pt, available from Strem(Dexler Industrial Park, 7 Mulliken Way, Newbury Mass.), in 30milliliters (ml) of distilled water.

The metal salt solution was added to 20.0 g of 12×40 mesh activatedcarbon granules contained in an evaporating dish. The granules had a BETsurface area in excess of 800 m² /g. The mixture was heated using asteam bath and continuously stirred until it became free flowing atwhich point the mixture was transferred to a 106 cm long×25 mm (outerdiameter) quartz tube. The quartz tube was placed in a three-elementelectric tube furnace so that the mixture was located substantially inthe center of the furnace heat zone. Nitrogen, at a flow rate of 100standard cubic centimeters per minute, was continuously passed throughthe catalyst bed while the tube was heated from ambient temperature to300° C. over a 2 hour period. The temperature was held at about 300° C.for 2 hours and then allowed to naturally cool back to ambienttemperature. The catalyst prepared in this manner, designated asCatalyst 1, contained 1.10 weight % platinum and had a density of 0.57g/ml.

Comparative Catalyst 1

A second catalyst, C-1, was prepared using the same procedure as aboveexcept 290 milligrams (mg), (1.18 millimoles, (mmol)) of nickel acetatetetrahydrate was used instead of dihydrogen hexachloroplatinate. Thecatalyst contained 0.34 weight % Ni.

Comparative Catalyst 2

A third catalyst, C-2, was prepared using the same procedure as aboveexcept 207 mg (1.17 mmol) of palladium chloride was used instead of thedihydrogen hexachloroplatinate. An additional 10 ml of concentrated HClwas added to the 30 ml of distilled water to solubilize the palladiumchloride. The catalyst contained 0.61 weight % Pd.

Comparative Catalyst 3

A fourth catalyst, C-3, was prepared using the same procedure as aboveexcept 418 mg (1.17 mmol) of iridium trichloride hydrate was usedinstead of the dihydrogen hexachloroplatinate. The catalyst contained1.10 weight % Ir.

Carbonylation of Methanol

In the examples which follow, the reactor consisted of a clean Hastelloyalloy tubing having dimensions of 800 to 950 mm (31.5 and 37 inch) longand an inside diameter of 6.35 mm (1/4 inch). The preheat andcarbonylation reaction zones of the reactor were prepared by insertinginto the tube a quartz wool pad approximately 410 mm from the top. Thequartz wool acted as a support for the catalyst. Adjacent to the quartzwool pad the following materials were added: (1) a 0.7 g bed of finequartz chips (840 microns); (2) 0.5 g of one of the above describedcatalysts; and (3) an additional 6 g of fine quartz chips which acted asa heat exchange surface to vaporize the liquid feeds. The top of thetube was attached to an inlet manifold for introducing liquid andgaseous feeds. The remaining lower length of tubing (product recoverysection) acted as a condenser and consisted of a vortex cooler whichvaried in length depending on the original length of tubing employed andwas maintained at approximately 0-5° C. during operation.

The gases were fed using Brooks flow controllers and liquids were fedusing a high performance liquid chromatography pump. Care was taken notto allow any liquid feeds to contact the solid catalyst materials at anytime, including assembly, start-up, and shutdown. The product reservoirtank was placed downstream from the reactor system. The pressure of thereactor was maintained using a Tescom 44-2300 pressure regulator on theoutlet side of the reactor system and the temperature of the reactionsection was maintained using heating tape on the outside of the tube.

Hydrogen and carbon monoxide were fed to the reactor when the reactorequilibrated at a temperature of about 240° C. and a pressure of 17.2bara (250 psia). The hydrogen flow rate was maintained at 25 standardcubic centimeters per minute (cc/min). The carbon monoxide flow rate wasmaintained at 100 cc/min. The reactor was maintained under theseconditions for 1 hour or until the temperature and pressure hadstabilized, whichever was longer. The high pressure liquidchromatography pump was then started, feeding at a rate of 10-12 g perhour a mixture consisting of 70 weight percent methanol and 30 weightpercent methyl iodide. Samples of the liquid product were collected andanalyzed as indicated in Table 1 using gas chromatographic techniquesknown to those skilled in the art.

Carbonylation Example 1

Samples of the product stream were taken as shown below during themethanol carbonylation for Catalyst I. The weight and composition of theeach sample are set forth in Table 1. "Time" is the total time ofoperation of carbonylation as measured from the feeding of methanoluntil the indicted sample was taken. The values for methyl iodide("MeI"), methyl acetate ("MeOAc"), methanol ("MeOH") and acetic acid("HOAc") are weight percent based on the total weight of these compoundsin the sample and were obtained using a flame ionization detector.

                  TABLE 1                                                         ______________________________________                                        Sample Time                               Sample                                Number (hours) MeI MeOAc MeOH HOAc (grams)                                  ______________________________________                                        1      4.00    16.96   4.93  62.55  0.78  30.2                                  2 5.50 17.64 8.03 59 1.6 23.5                                                 3 8.50 18.33 17.58 46.45 5.17 24.1                                            4 12.00 18.32 17.46 46.01 5.11 48.9                                           5 16.00 16.38 16.21 53.22 3.78 70.1                                           6 19.00 16.41 16.23 53.96 3.74 28.3                                           7 24.00 14.26 26.74 35.1 10.77 20.2                                           8 27.00 19.73 36.31 7.47 19.39 30.9                                           9 28.50 16.88 27.32 37.79 4.52 26.4                                           10 32.50 20.76 35.61 5.53 21.61 48.6                                          11 34.50 20.75 35.6 5.53 21.64 22.9                                           12 40.00 12.59 11.78 65.13 2.04 70.4                                          13 43.00 12.46 11.73 65.01 2.03 22.1                                          14 48.00 15.13 22.49 42.36 7.88 49                                            15 50.00 17.14 29.76 23.07 15.83 28.5                                       ______________________________________                                    

The rate of acetyl production based on the preceding experimentutilizing Catalyst I is set forth in Table 2 below. The Sample Numberand Time values correspond to those of Table 1. "Acetyl Produced"represents the quantity, in millimoles, of methyl acetate and aceticacid produced during each increment of Time. Acetyl Produced iscalculated from the formula:

    Acetyl Produced=(Sample weight (grams))×10×((weight % of MeOAc/74)+(weight % of AcOH/60)).

"Production Rate" is the moles of Acetyl Produced per liter of catalystvolume per hour during each increment of Time (Time Increment), i.e.,the time of operation between samples. The formula for determining molesof Acetyl Produced per liter of catalyst volume per hour is determinedas follows:

    0.57×Acetyl Produced/(0.5×Time Increment)

wherein 0.5 is the grams of catalyst used and 0.57 is the density of thecatalyst in g/mL.

                  TABLE 2                                                         ______________________________________                                                      Acetyl                                                            Sample Produced Rate                                                          Number (mmol) (mol/L-h)                                                     ______________________________________                                        1             24.0     6.9                                                      2 31.8 24.1                                                                   3 78.0 29.6                                                                   4 157.0 51.1                                                                  5 197.7 56.4                                                                  6 79.7 30.3                                                                   7 109.3 24.9                                                                  8 251.5 95.6                                                                  9 117.4 89.2                                                                  10 408.9 116.5                                                                11 192.8 109.9                                                                12 136.0 28.2                                                                 13 42.5 16.2                                                                  14 213.3 48.6                                                                 15 189.8 108.2                                                              ______________________________________                                    

Over the 50 hours of testing, the catalyst produced 2.23 moles ofacetyl. This represents a rate of 89 moles of acetyl per kilogram ofcatalyst per hour (acetyl/kg_(cat) -h) or, represented as an hourlyspace velocity, 45 mol of acetyl/L_(cat) -h.

Comparative Carbonylation Examples 1-3

Comparative catalysts, C-1, C-2 and C-3 above were used in thecarbonylation of methanol using the same procedure and parameters asdescribed above. The Production Rate, expressed in terms of moles ofAcetyl Produced per kilogram of catalyst per hour and moles per liter ofcatalyst volume per hour, for Catalyst 1 and Comparative catalystsC-1-C3 is shown in Table 3 below. As can be seen from Table 3, theplatinum catalyst is nearly 30 times more active for the vapor phasecarbonylation of methanol than Ni, or Pd. Comparative Example C-3demonstrates that rates with platinum on activated carbon are comparableto those obtained with Ir on an activated carbon support. This is quiteunexpected in view of Yagita and Fujimoto, Journal of MolecularCatalysis, 69, 191-197 (1991), discussed above.

                  TABLE 3                                                         ______________________________________                                        Carbonylation         Production Rate                                         Example     Catalyst  moles/kg.sub.cat -h                                                                     moles/L.sub.cat -h                            ______________________________________                                        1            1 (Pt)   89        45                                              C-1 C-2 (Pd) 3 1.7                                                            C-2 C-3 (Ni) 1.4 0.8                                                          C-3 C-4 (Ir) 93 53                                                          ______________________________________                                    

Although the present invention has been shown and described in terms ofthe presently preferred embodiment(s), it is to be understood thatvarious modifications and substitutions, rearrangements of parts,components and process steps can be made by those skilled in the artwithout departing from the novel spirit and scope of the invention.

We claim:
 1. A vapor-phase carbonylation method for producing esters andcarboxylic acids from reactants selected from the group consisting oflower alkyl alcohols having from 1 to 10 carbon atoms, alkane polyolshaving 2 to 6 carbon atoms, alkyl alkylene polyethers having 3 to 20carbon atoms alkoxyalkanols having from 3 to 10 carbon atoms andmixtures thereof, said process comprising contacting the reactants withcarbon monoxide in a carbonylation zone of a carbonylation reactor andunder vapor-phase conditions with a catalyst consisting of from about0.01 weight percent to about 10 weight percent platinum on a solidsupport material and a vaporous second component comprising a halide. 2.The method of claim 1 wherein said catalyst has from about 0.1 weightpercent to about 2 weight percent platinum.
 3. The method of claim 1wherein said vapor-phase carbonylation has a pressure of from about 0.1bar to 100 bars and a temperature of from about 100° C. to about 350° C.4. The method of claim 1 wherein said vapor-phase carbonylation has apressure of from about 1 bar to about 50 bar and a temperature of fromabout 150° C. to about 275° C.
 5. The method of claim 1 wherein saidvapor component is at least one halide selected from the groupconsisting of chlorine, bromine and iodine.
 6. The method of claim 5wherein said at least one halide is selected from hydrogen halides,alkyl, aryl halides having up to 12 carbon atoms, and mixtures thereof.7. The method of claim 6 wherein said at least one halide is selectedfrom as hydrogen iodide, gaseous hydriodic acid, methyl iodide, ethyliodide, 1-iodopropane, 2-iodobutane, 1-iodobutane, hydrogen bromide,methyl bromide, ethyl bromide, benzyl iodide, and mixtures thereof. 8.The method of claim 6 wherein said at least one halide is selected fromhydrogen iodide, methyl iodide, hydrogen bromide, methyl bromide, andmixtures thereof.
 9. A vapor-phase carbonylation method for producingesters, carboxylic acids and mixtures thereof from reactants selectedfrom the group consisting of lower alkyl alcohols having from 1 to 10carbon atoms, alkane polyols having 2 to 6 carbon atoms, alkyl alkylenepolyethers having 3 to 20 carbon atoms alkoxyalkanols having from 3 to10 carbon atoms and mixtures thereof, said process comprising contactingsaid reactants and carbon monoxide with a catalyst system in acarbonylation zone; and recovering a gaseous product from thecarbonylation zone, wherein said catalyst system consisting of fromabout 0.01 weight percent to about 10 weight percent platinum on anactivated carbon support and a vaporous second component comprising ahalide selected from the group consisting of chlorine, bromine andiodine.
 10. The method of claim 5 wherein said at least one halide isselected from hydrogen halides, alkyl halides and aryl halides having upto 12 carbon atoms, and mixtures thereof.
 11. The method of clam 9wherein said reactant is methanol.
 12. The method of claim 9 whereinsaid reactant is dimethyl ether.
 13. A vapor-phase carbonylation methodfor producing acetic acid and methyl acetate comprising contacting agaseous mixture comprising methanol and carbon monoxide with a catalystsystem in a carbonylation zone; and recovering a gaseous product fromthe carbonylation zone wherein said catalyst system consisting of fromabout 0.01 weight percent to about 10 weight percent platinum on carbonsupport and a vaporous second component selected from hydrogen iodide,methyl iodide, hydrogen bromide, methyl bromide, and mixtures thereof.14. The method of claim 13 wherein said catalyst has from about 0.01weight percent to about 10 weight percent platinum.
 15. The method ofclaim 13 wherein said at least one halide is selected from hydrogeniodide, methyl iodide, hydrogen bromide, methyl bromide, and mixturesthereof.